Thin-film deposition techniques are generally used to deposit a semiconductor material onto a substrate for manufacturing integrated circuit devices or optoelectronic devices. For instance, MOCVD is a method of depositing a semiconductor material such as gallium nitride (GaN) on a substrate. The MOCVD method is performed in a reactor with a temperature-controlled environment to activate the deposition of precursor gases on a heated substrate arranged in the reactor whilst reducing the parasitic deposition of the precursor gases on unwanted areas such as on the chamber walls, which are cooler. A first precursor gas includes a Group III element such as gallium (Ga), while a second precursor gas includes a Group V element such as nitrogen (N). These precursor gases are introduced into the reactor to deposit a compound semiconductor such as GaN on a planar surface of the heated substrate. Purging gases such as nitrogen (N2) and hydrogen (H2) are also introduced into the reactor to minimise the deposition of the precursor gases on the unwanted areas within the reactor. Carrier gases such as N2 and H2 are used during the MOCVD operation to move the precursor gases towards the heated substrate.
Typically, the precursor gases are introduced into the reactor in a direction perpendicular or parallel to the planar surface of the heated substrate. In order to ensure that the precursor gases chemically react on the major planar surface of the heated substrate to form the compound semiconductor, these precursor gases have to be close to each other on top of the substrate surface. One problem that arises when the precursor gases are close to each other when they are introduced into the reactor is that an undesirable mutual gas phase reaction takes place which compromises the efficiency of the precursors and consequently the quality of the compound semiconductor deposited on the substrate.
Thus, it is an object of this invention to address the limitation associated with the conventional way of introducing precursor gases into a reactor among thin-film deposition techniques, and particularly among chemical vapour deposition (CVD) techniques.